The competition between superconductivity and ferromagnetism in small metallic grains: thermodynamic properties

TL;DR

This paper investigates how ferromagnetic exchange interactions influence the thermodynamic properties of small superconducting metallic grains, revealing different effects in BCS and fluctuation-dominated regimes.

Contribution

It introduces a quantum Monte Carlo approach to analyze the interplay between superconductivity and ferromagnetism in small metallic grains using the universal Hamiltonian.

Findings

Exchange interactions alter thermodynamic signatures of pairing.

Different effects observed in BCS vs. fluctuation regimes.

Quantum Monte Carlo effectively captures these phenomena.

Abstract

We study the thermodynamic properties of a small superconducting metallic grain using a quantum Monte Carlo method. The grain is described by the universal Hamiltonian, containing pairing and ferromagnetic exchange correlations. In particular, we study how the thermodynamic signatures of pairing correlations are affected by the spin exchange interaction. We find the exchange interaction effects to be qualitatively different in the BCS and fluctuation-dominated regimes of pairing correlations.